Thanks to improved storage capacity, more frequent recharging capability and higher energy densities, metal-oxygen based batteries such as batteries based on lithium-oxygen cells are finding more and more applications. Batteries based on metal-oxygen cells are distinguished by high energy densities and an extremely low self-discharge, among other things.
Batteries with lower energy storage capacity are used, for example, for small portable electronic devices such as mobile telephones, laptops, camcorders and the like, while batteries with high capacity find use as an energy source to power the engines of motor vehicles, especially hybrid or electric vehicles etc., or as stationary energy storages, such as for systems extracting regenerative forms of energy.
If metal electrode and air electrode of a metal-oxygen cell are connected in electrically conducting manner to a consumer, the negatively charged metal ions flow from the metal electrode to the air electrode. At the same time, the metal ions flow through the electrically conductive electrolyte. This brings about a reaction with oxygen. When charging the metal-oxygen cell, this process occurs in the opposite direction, releasing once more the previously bound oxygen. Metal-oxygen cells enable relatively high energy densities, since the oxygen need not be contained in the battery itself, but instead can be supplied from the surroundings.
In a closed system, therefore, the quantity of oxygen in the system decreases during the discharging and increases again during the charging.
In an open system, ambient air can serve as the oxygen source, while in the case of lithium-oxygen cells in particular one must make sure that only oxygen, but not the humidity or other impurities are supplied to the cell. According to the prior art, as documented for example in WO 2011/052440 A1, lithium-oxygen cells therefore comprise a membrane, which is especially impervious to water and/or water vapor and preferably permeable to oxygen.
A lithium-oxygen cell is known from US 2009/0239132 A1, having an air inlet and an air outlet. The air inlet line here comprises an H2O and CO2 separator.
US 2012/0041628 A1 deals with a metal-air battery, wherein an oxygen concentration is maintained constant during the charging of the battery. The oxygen supply comes from a tank, the oxygen being led in a circuit or given off to the ambient air.